Conversion of analog images into digital data has become widespread for a variety of applications, including storing, manipulating, transmitting and displaying or printing copies of the images. For example, sequences of frames from a motion picture film are often digitized, image enhancement or special effects are performed on the digitized images, and the result written onto a blank film. Also, images captured on photographic media are converted to digital data and stored for readout and display as an image and/or for printing with various types of printer. In order to capture the photographic image digitally, the film frame is scanned with a light beam, and the light transmitted through the film is detected, typically as three primary colour red, green, blue (RGB) light intensity signals, and digitized. The digitized values may be formatted to a standard for video display and stored on compact disc, solid state or magnetic media. Such film digitizers take a variety of forms and the various common aspects of film digitizing, particularly line illumination and linear CCD-based digitizers, are described in greater detail in commonly assigned U.S. Pat. No. 5,012,346, incorporated herein by reference. Photographic prints can also be digitized using reflection scanners.
Part of the image can be damaged by scratches or degraded by dust. Providing replacement pixel values for corrupted, damaged or otherwise defective pixels is a common operation in digital image processing. New pixel values must be supplied more or less consistent with the image content surrounding the area of the actual defective pixels to be replaced. Another example of an image processing operation requiring pixel replacement is removal of an object from the image, for example microphone, rig and wire removal in motion pictures. Thus, ‘defect’ as used herein includes unwanted pixel values as well as corrupted, damaged or absent ones.
Jia and Tang, “Image Repairing: Robust Image Synthesis by Adoptive ND Tensor Voting”, Proceedings IEEE CVPR, 2003 propose a defect correction algorithm which samples replacements for a defect pixel from the remaining image. It is desirable to provide defect correction having reduced computation requirements, while making use of colour information.